Studies in pediatric blood disorders provide an important paradigm for understanding the fundamental mechanisms regulating hematopoiesis. Unlike adult hematologic disorders, many pediatric diseases result from intrinsic genetic defects that control blood cell development or function. Very little is understood about the molecular pathogenesis of many of the hematologic diseases in children. At UCLA, we have a tremendous resource of interdisciplinary investigators whose research focuses on a wide spectrum of topics related to developmental hematology. Therefore, we propose a unique training program that focuses specifically on pediatric hematologic diseases by integrating a variety of disciplines, including molecular and cellular hematopoiesis, alternative organism models, stem cell transplantation, hemostasis and thrombosis, transfusion medicine, novel technologies in proteomics/genomics, hematologic malignancies, therapeutics, and mathematical modeling. Given the declining number of physician-scientists in Pediatric Hematology, a training program in Developmental Hematology is critical to advance the field. In this application, we seek funding for 4 postdoctoral fellows per year for 5 years. The fellows will be either MDs, MD/PhDs, or PhDs. Trainees will have the opportunity to develop research in one of the 22 faculty member's laboratories. Trainees will be selected from a pool of approximately 20 to 30 postdoctoral fellows based on their academic potential and research achievements. Appointments will be for two years, the second year appointment being dependent on a progress report. Trainees will be required to participate in multidisciplinary journal clubs, a course on coagulation, and seminars. They will also take a required course on Developmental Hematology through the Department of Pathology. Pediatric Hematology/Oncology trainees will be expected to meet with their Scholarship Oversight Committees every 6 months to monitor progress and productivity. They will present their work at national meetings. Many investigators have pre- existing collaborations and publications. We hope to utilize the strengths of UCLA, including the breadth and depth of investigators across many disciplines, to train future researchers and leaders in the field of Pediatric Hematology.